Sorry if this is a stupid question but I am not a weapons expert and just started shooting seriously. Recently bought some F1 62grain ammo (1,000 rounds). I specifically bought this ammo because I wanted a slightly higher grain that weren't green tip (although I'm sure the grain doesn't make that much of a difference). Anyway, I got the ammo yesterday and the casing seems to be eroded (very gray looking instead of the brass look). I shot a few rounds off, and the gun smells very gassy when pulling the charging handle back, and to add to that, the charging handle is very stiff after shooting, it was taking me a lot of force to pull the charging handle back even though I only shot off a few rounds to test the ammo out. I'm just curious if the ammo is okay to shoot? I've put some gun oil down in the gun so hopefully that will resolve the stiffness issue.